# \#power

**URL:** https://discourse.datamethods.org/tag/power/77.md

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## [Use of cpower function in Hmisc package](https://discourse.datamethods.org/t/use-of-cpower-function-in-hmisc-package/7345)

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**Author:** [@jlevy13](https://discourse.datamethods.org/u/jlevy13)\
**Replies:** 7\
**Last updated:** [August 22, 2026, 11:04am UTC](https://discourse.datamethods.org/t/use-of-cpower-function-in-hmisc-package/7345 "2026-08-22T11:04:32Z")

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I am trying to calculate the power for Cox PH analysis using the cpower function in the Hmisc package. The following is sort of “post-hoc power”, mainly to understand how the function works. There are 2 groups, with 250…

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## [BBR Session 11: Nonparametric Tests Using the Proportional Odds Model](https://discourse.datamethods.org/t/bbr-session-11-nonparametric-tests-using-the-proportional-odds-model/2915)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 21\
**Last updated:** [June 6, 2025, 1:43pm UTC](https://discourse.datamethods.org/t/bbr-session-11-nonparametric-tests-using-the-proportional-odds-model/2915 "2025-06-06T13:43:30Z")

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This is a place for questions, answers, and discussion about session 11 of the Biostatistics for Biomedical Research airing 2020-01-24 introducing the proportional odds model as a generalization of the Wilcoxon and Krusk…

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## [Sample Size in crossover trials](https://discourse.datamethods.org/t/sample-size-in-crossover-trials/19269)

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**Author:** [@trumanfrancis](https://discourse.datamethods.org/u/trumanfrancis)\
**Replies:** 4\
**Last updated:** [August 29, 2024, 12:23pm UTC](https://discourse.datamethods.org/t/sample-size-in-crossover-trials/19269 "2024-08-29T12:23:39Z")

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Are there any references for calculating sample size in a crossover trial. Thanks

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## [Justification of sample size for the generation of a prediction model](https://discourse.datamethods.org/t/justification-of-sample-size-for-the-generation-of-a-prediction-model/6343)

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**Author:** [@a\_j](https://discourse.datamethods.org/u/a_j)\
**Replies:** 7\
**Last updated:** [January 11, 2023, 12:53pm UTC](https://discourse.datamethods.org/t/justification-of-sample-size-for-the-generation-of-a-prediction-model/6343 "2023-01-11T12:53:21Z")

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Dear all, I plan a retrospective analysis of patients who visited our outpatient clinic. The data will be extracted from our hospital information system. One specific research question is to generate a prognostic model …

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## [Power analysis in observational studies](https://discourse.datamethods.org/t/power-analysis-in-observational-studies/4095)

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**Author:** [@arthur\_albuquerque](https://discourse.datamethods.org/u/arthur_albuquerque)\
**Replies:** 13\
**Last updated:** [July 26, 2022, 1:09pm UTC](https://discourse.datamethods.org/t/power-analysis-in-observational-studies/4095 "2022-07-26T13:09:47Z")

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Does anyone have a good reference about power analysis in observational studies, mostly retrospective ones? I have read conflicting opinions on this topic.

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## [Determine power to detect a misclassification event in rule-out pathways for myocardial infarction](https://discourse.datamethods.org/t/determine-power-to-detect-a-misclassification-event-in-rule-out-pathways-for-myocardial-infarction/5258)

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**Author:** [@tomkaier](https://discourse.datamethods.org/u/tomkaier)\
**Replies:** 10\
**Last updated:** [January 15, 2022, 11:32pm UTC](https://discourse.datamethods.org/t/determine-power-to-detect-a-misclassification-event-in-rule-out-pathways-for-myocardial-infarction/5258 "2022-01-15T23:32:32Z")

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The question concerns work we have recently conducted, looking at risk prediction using a serum biomarker in a study population presenting with chest pain to emergency departments. In clinical medicine, biomarkers such a…

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## [Statistical conundrum: multiple noisy measurements vs an oracle](https://discourse.datamethods.org/t/statistical-conundrum-multiple-noisy-measurements-vs-an-oracle/4438)

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**Author:** [@Granville\_Matheson](https://discourse.datamethods.org/u/Granville_Matheson)\
**Replies:** 7\
**Last updated:** [May 24, 2021, 8:26pm UTC](https://discourse.datamethods.org/t/statistical-conundrum-multiple-noisy-measurements-vs-an-oracle/4438 "2021-05-24T20:26:04Z")

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I have a bit of a statistical conundrum that I can’t quite wrap my head around. It appears very simple, but the results are very counterintuitive, and I just can’t find an intuitive explanation. This all originated with…

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## [Value stream mapping - numbers needed](https://discourse.datamethods.org/t/value-stream-mapping-numbers-needed/4120)

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**Author:** [@kiwiskiNZ](https://discourse.datamethods.org/u/kiwiskiNZ)\
**Replies:** 0\
**Last updated:** [February 8, 2021, 9:17pm UTC](https://discourse.datamethods.org/t/value-stream-mapping-numbers-needed/4120 "2021-02-08T21:17:48Z")

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I was just asked for a power-calculation for a Value stream mapping proposal. Very odd. However, it got me thinking. If, as in this case, we are looking at time spent with a patient by different medical staff in an em…

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## [Power Analysis for 3 Groups and 3 Measures](https://discourse.datamethods.org/t/power-analysis-for-3-groups-and-3-measures/4116)

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**Author:** [@EriMal](https://discourse.datamethods.org/u/EriMal)\
**Replies:** 1\
**Last updated:** [February 7, 2021, 12:03pm UTC](https://discourse.datamethods.org/t/power-analysis-for-3-groups-and-3-measures/4116 "2021-02-07T12:03:10Z")

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My study “needs to be powered to detect individual group comparisons, not simply the omnibus ANOVA because this is where the hypotheses will ultimately be tested” (feedback I received from a proposal reviewer). The hypot…

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## ["Observed Power" and other "Power" Issues](https://discourse.datamethods.org/t/observed-power-and-other-power-issues/731)

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**Author:** [@ADAlthousePhD](https://discourse.datamethods.org/u/ADAlthousePhD)\
**Replies:** 74\
**Last updated:** [September 6, 2020, 9:26pm UTC](https://discourse.datamethods.org/t/observed-power-and-other-power-issues/731 "2020-09-06T21:26:20Z")

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@zad, I saw this comment of yours on Andrew Gelman’s website and wondered if you would be willing to discuss here: “I submitted something similar to JAMA last month regarding a trial that investigated the effects of an …

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## [Power calculations for cluster-RCT in hospital infection control (PPE for Covid19)](https://discourse.datamethods.org/t/power-calculations-for-cluster-rct-in-hospital-infection-control-ppe-for-covid19/3161)

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**Author:** [@Raj](https://discourse.datamethods.org/u/Raj)\
**Replies:** 6\
**Last updated:** [April 1, 2020, 3:14pm UTC](https://discourse.datamethods.org/t/power-calculations-for-cluster-rct-in-hospital-infection-control-ppe-for-covid19/3161 "2020-04-01T15:14:29Z")

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Given the current COVID19 pandemic, having an RCT that could evaluate efficacy of PPE (personal protective equipment) would be of value to determine safety needs of Health care workers. However, previous sample calculat…

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## [What to interpret when observed effect size is smaller but statistically significant than expected effect size](https://discourse.datamethods.org/t/what-to-interpret-when-observed-effect-size-is-smaller-but-statistically-significant-than-expected-effect-size/675)

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**Author:** [@Madhu](https://discourse.datamethods.org/u/Madhu)\
**Replies:** 18\
**Last updated:** [January 29, 2020, 2:38pm UTC](https://discourse.datamethods.org/t/what-to-interpret-when-observed-effect-size-is-smaller-but-statistically-significant-than-expected-effect-size/675 "2020-01-29T14:38:25Z")

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I read a recent clinical trial where the researchers powered their study (80%) for an expected effect size of 4% absolute risk reduction. With the same sample size, they, however, report an absolute risk reduction of 3%,…

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## [Bayesian Power: No Unobservables](https://discourse.datamethods.org/t/bayesian-power-no-unobservables/1849)

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**Author:** [@f2harrell](https://discourse.datamethods.org/u/f2harrell)\
**Replies:** 6\
**Last updated:** [July 8, 2019, 6:16pm UTC](https://discourse.datamethods.org/t/bayesian-power-no-unobservables/1849 "2019-07-08T18:16:17Z")

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Most statisticians I’ve spoken with who frequently collaborate with investigators in doing frequentist power calculations believe that the process is nothing more than a game or is voodoo. Minimal clinically important e…

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## [Power calculations for non-parametric data](https://discourse.datamethods.org/t/power-calculations-for-non-parametric-data/150)

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**Author:** [@trumanfrancis](https://discourse.datamethods.org/u/trumanfrancis)\
**Replies:** 3\
**Last updated:** [July 25, 2018, 11:19am UTC](https://discourse.datamethods.org/t/power-calculations-for-non-parametric-data/150 "2018-07-25T11:19:34Z")

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Can you use Monte Carlo simulation to calculate sample size for a non-parametric test like a one way analysis of variance?